KJS: don't overwrite prototype of native classes when inheriting from them

js/js.translator/testData/box/inheritance/nativeNativeKotlin.kt

@@ -0,0 +1,45 @@
+// FILE: nativeNativeKotlin.kt
+
+package foo
+
+@native
+open class A {
+    fun foo(): String
+}
+
+@native
+open class B : A() {
+    fun bar(): String
+}
+
+class C : B()
+
+fun box(): String {
+    val c = C()
+
+    assertEquals("A.foo", c.foo())
+    assertEquals("B.bar", c.bar())
+
+    return "OK"
+}
+
+// FILE: nativeNativeKotlin.js
+
+function A() {
+
+}
+
+A.prototype.foo = function () {
+    return "A.foo"
+};
+
+function B() {
+
+}
+
+B.prototype = Object.create(A.prototype);
+B.prototype.constructor = B;
+
+B.prototype.bar = function () {
+    return "B.bar"
+};